HIV Can Re-Emerge From a Single Cell

MONDAY Oct. 20, 2008 -- It's been a mystery for medical researchers: How does the AIDS virus bring itself back to life after powerful drugs allow infected people to eliminate all signs of the disease in their blood?

Now, new research suggests HIV can hibernate inside a small number of cells -- or even a single cell -- until re-emerging to wreak havoc.

Study co-author Huldrych Gunthard, a researcher at University Hospital Zurich, in Switzerland, said the findings are actually good news, because they suggest that the virus isn't replicating itself while dormant. That could mean that AIDS patients who adhere to their drug regimens as prescribed will avoid having to fight a newly strengthened virus.

"It is a very good message for patients and doctors," Gunthard said.

While drugs available since the mid-1990s have allowed many AIDS patients to reduce the level of the virus in their blood to zero, the disease remains incurable. According to Gunthard, the virus can hide in the lymphatic system -- which includes lymph nodes, the spleen and other organs -- and in the brain and bone marrow, among other places.

Doctors generally urge AIDS patients to take their medication on a regular basis, because the virus can make a dramatic -- and potentially deadly -- reappearance if there aren't drugs in the body to keep it at bay.

In the new study, Gunthard and colleagues examined the AIDS virus from 20 patients who had gone off their medications for two weeks at a time as part of a study. By examining how the virus evolved over time, the researchers found that the disease can emerge from a small number of cells, or even a single one, when medication is stopped.

"This is actually very surprising, if one considers that there are millions of cells in the body from which the infection can take off," Gunthard said.

The research, published in this week's Proceedings of the National Academy of Sciences, also suggests that the virus doesn't evolve into new forms while patients aren't taking AIDS drugs. Evolution of the virus can lead to new forms that aren't as susceptible to drugs.

"This is a very good finding and suggests that our treatments are really very potent, and the effects will be long lasting," Gunthard said.

Dr. Jeffrey Laurence, director of the Laboratory for AIDS Virus Research at Weill Medical College of Cornell University, said the new findings reflect the findings of other research.

"These studies imply that current anti-HIV drug regimens are about as potent as they can be, completely blocking viral replication, and thus cell-to-cell transmission of virus," he said. "Therefore, any virus measured in the blood of a patient on long-term therapy -- assuming they are adherent to their medications -- most likely comes only from cells infected prior to the start of HIV treatment."